1. Field of the Invention
The invention relates generally to apparatus for connecting heat exchanger tubes to the bulkheads of heating vessels, such as deep fat fryer cooking vessels. In particular, the invention relates to connectors for joining heat exchanger tubes to the bulkheads of fryer vessels so as not to interfere with the insertion of racks and other food product holding apparatus into the fryer. Moreover, the invention particularly relates to cooking apparatus including such connectors and to connector housings used in the fabrication of such connectors.
2. Description of Related Art
Commercial users of open well and pressure fired fryers have become increasingly aware of the costs associated with operating and maintaining their equipment. Unfortunately, existing devices have significant disadvantages in the areas of thermal efficiency and maintenance and repair. In particular, conventional techniques of welding fryer heating vessels and heat exchanger apparatus together makes their maintenance more expensive. Specifically, both the fryer heating vessels and heat exchanger apparatus may require replacement in order to repair or replace a portion of the fryer, causing existing devices to have high maintenance costs.
Heat exchanger apparatus including interior conduit for heated combustion products are frequently used in flyer heating vessels. An example of such an interior heating system is described in U.S. Pat. No. 4,751,915. A conduit through the lower portions of the vessel carries heated combustion products from the front wall to the rear wall of the vessel. These straight heat exchanger tubes may operate in a low pressure system with burner pressures in a range of about 0.25" water column to about 0.50" water column.
Unfortunately, uniform temperature control is not achieved with such systems. The cooking medium, such as cooking oil, in the lower region of the vessel may have a higher temperature because of its proximity to the straight heat exchanger tubes. Some interior heating systems also may have only a single direction of flow for combustion products. Because combustion products cool as they transfer heat to the cooking medium, such straight heat exchanger tubes tend to transfer more heat to the front portion of the vessel than to the rear potion. These factors may combine to produce erratic and non-uniform temperature distributions. High and nonuniform temperatures also may cause excessive thermal stresses to develop in the vessel walls and any welds therein. Subsequent structural fatigue of the vessel wall may increase the frequency of necessary vessel replacement.
As described in U.S. Pat. No. 5,402,713, the disclosure of which is incorporated herein by reference, a deep fat fryer vessel may include an interior array for heat exchanger tubes arranged in a U-shaped configuration along the sides and rear of the vessel. Referring to FIG. 1, heat exchanger tubes 2 may be positioned in the interior of the vessel 1 with the ends attached to the front vessel bulkheads by means of a mechanical fastening on the exterior side of the vessel bulkhead and a seal on the interior side of the vessel bulkhead. Referring to FIGS. 2 and 3, a bulkhead fitting 3 may be welded to the ends of two heat exchanger tubes 2 secured to the interior of the vessel by fasteners 17.
Each heat exchanger tube may employ one or more premix burner components which fire directly into the heat exchanger tube from one end. Each heat exchanger tube also may have its burners on either end of the tube. The combustion gases produced by the burners travel through the heat exchanger tube and exit into a combustion channel. Tubes 2 may be shaped and arranged to provide adequate space in vessel 1 to insert a rack 4 for holding food products into the center of the U-shaped tube configuration. The combustion channel directs the gases exiting the heat exchanger tube around and in contact with at least a portion of the exterior wall of the vessel and then to an exhaust flue at the rear of the vessel.